Poster Session: Graduate

Transcription

1 SPC-5 Braze-ability of Silver-based Brazing Filler Alloy (Ag-Cu-Cd-Zn) Jun Sokawa, Hitoshi Maruyama, Maki Nozue, Yasayuki Miyazawa, Tadashi Ariga, Tokai University Introduction Ag-based brazing filler alloy are used for joining most ferrous and nonferrous metals, except Al and Mg. This classification includes a range of silver based filler metal compositions which may have various additions such as Cu, Zn, Cd, Sn, Mg, Ni and Li. Generally speaking, the addition of Zn lowers the melting temperature of the Ag-Cu binary alloys and helps wet Fe, Co and Ni. Cd is also effective in lowering the brazing temperature of these alloys and assists in wetting a variety of base metals. Especially, Cd and Zn are vaporized during brazing. Much attention has been paid to a few kinds of poisonous elements such as Cd, Pb, and so on in recent years. Especially, the concern about Cd element came to be had especially in general with Itai-Itai disease in May 968 as a start. On the other hand, Cd content Ag-based brazing filler metal has excellent brazed-ability in general. There are a variety of kinds of Ag-based brazing filler metal. JIS standard has four kinds of Ag-based brazing filler metal containing Cd (BAg-, BAg-A, BAg-, and BAg- 3) as shown in Table. Therefore the development of Cd-free silver brazing alloy is needed. However, effect of various additions, especially Cd, is not cleared. So that effect of various additions of Ag-based brazing filler alloy to brazeability was investigated. Brazeability of this filler was estimated by cross-sectional microstructure and spreading test to look for the element that became substitution of Cd.

2 Table. Chemical compositions of temperature characteristic of Ag-based brazing filler metal containing Cd in JIS standard Class Chemical compositions (mass%) Temperature ( C) Ag Cu Zn Cd Ni Others Solidus Liquidus Brazing range BAg Under BAg-A Under BAg Under BAg Under BAg Under BAg Bal. - - Under Procedures Spreading test Pure copper plate (30mm X 30mm, 0.5mm thickness) was employed as a base metal. BAg-, BAg-A, BAg-, and BAg-3 were used as brazing filler metal. BAg-5 and BAg-8 were used as Ag-based brazing filler metal no containing Cd. Brazing filler metal in constant amount (0.g) were placed on pure copper plate (30mm X 30mm, 0.5mm thickness). The specimen was heated at 50K above the each brazing filler metal liquidus temperature for 5min during spreading test in an Ar gas atmosphere by using general horizontal furnace. And then the specimen was rapidly quenched into water. After quenching, spreading specimen was observed with the naked eye. And then the specimen, especially specimen surface, was observed with microscope. And then the microstructure and the elemental distributions at the edge of spread area, in other words, frontier of spread area, were observed and analyzed with FESEM-EDX examination to investigate the effect of Cd on wettability of molten Ag-based brazing filler metal to pure copper. Results and Discussions Figure showed the appearance of the specimen made by BAg- and Scanning Electron Microscope image and the Energy Dispersive X-ray Spectroscopy analysis results at the edge of spread area. And Figure showed high magnification SE image and EDX analysis results at the edge of spread area, which was corresponded to area 6 in Fig.. According to Fig., area was located at pure copper plate surface, area, 3, 4 were located at the edge of spread area and area 5 was located at brazing filler metal. Neither Ag nor Cd was detected at area,, 3, and 4. And Zn was detected at all area. And from Fig., area and were located at the edge of spread area, and area 3, 4, and 5 were located at brazing filler metal. Neither Ag nor Cd was detected at area and. And Zn was detected at all area. Therefore it was appeared that Zn spread preferentially and Zn influenced wetting phenomenon of BAg- brazing filler metal.

3 mm mm Ag Cu Zn Cd Figure. The appearance of the specimen made by BAg- and SE image and EDX analysis results at the edge of spread area

4 Ag Cu Zn Cd µm Figure. High magnification SE image and EDX analysis results at the edge of spread area, which was corresponded to area 6 in Fig. In that case of BAg-5, similar results was obtained. So that it was appeared that Zn spread preferentially and Zn influenced wet phenomenon of BAg-5 brazing filler metal. Figure 3 showed the appearance of the specimen made by BAg-8 and Scanning Electron Microscope image and the Energy Dispersive X-ray Spectroscopy analysis results at the edge of spread area. According to Fig.3, area and were located at brazing filler metal, area 3 and 4 were located at the edge of spread area, and area 5 was located at pure copper plate surface. And Ag was detected slightly at area 3 and 4. Therefore it was appeared that Ag spread preferentially and Ag influenced wetting phenomenon of BAg-8 brazing filler metal. Conclusions. It was appeared that Zn spread preferentially and Zn influenced wetting phenomenon of BAg- and BAg-5 brazing filler metal.. It was appeared that Ag spread preferentially and Ag influenced wetting phenomenon of BAg-8 brazing filler metal.

5 mm 00µm Ag Cu O Figure 3. The appearance of the specimen made by BAg-8 and SE image and EDX analysis results at the edge of spread area